Convection cooled fuse

ABSTRACT

An electric fuse adapted to be cooled by a flow of cooling medium in axial direction flowing through the center of the fuse, the ribbon fuse links being arranged in close proximity to the radially outer surface of the passageway means for the cooling fluid to maximize the heat exchange between the cooling medium and the ribbon fuse link.

United States Patent Jacobs, Jr.

151 3,693,128 51 Sept. 19, 1972 CONVECTION COOLED FUSE [72] Inventor: Philip C. Jacobs, Jr., Newtonville,

Mass.

[73] Assignee: The Chase-Shawmut Company,

Newburyport, Mass.

[22] Filed: Dec. 28, 1970 [211 App]. No.: 102,255

[52] US. Cl. ..337/166, 337/231, 337/247 [51] Int. Cl....H01h 85/04, H0lh 85/10, H0lh 85/14 [58] Field of Search ..337/154, 166, 231, 297

[56] References Cited UNITED STATES PATENTS 3,251,968 5/1966 Cameron ..337/166 UX 3,011,038 11/1961 Smith ..337/166 UX 3,538,479 1l/l970 Foster ..337/166 3,197,592 7/1965 Kozocka ..337/166 X 2,326,257 8/1943 Schmidt et a1 ..337/166 3,253,106 5/1966 l-iolsinger ..337/159 3,453,579 7/1969 Cinquin ..337/166 UX 2,777,033 l/l957 Kozocka ..337/159 Primary ExaminerBemard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorney-Erwin Salzer [5 7] ABSTRACT An electric fuse adapted to be cooled by a flow of cooling medium in axial direction flowing through the center of the fuse, the ribbon fuse links being arranged in close proximity to the radially outer surface of the passageway means for the cooling fluid to maximize the heat exchange between the cooling medium and the ribbon fuse link.

3 Claims, 4 Drawing Figures PATENTED 19 I97? 3 693. 128

FIG. I

INVENTOR= PHILIP C. JACOBS, JR.

1 CONVECTION COOLED FUSE BACKGROUND OF THE INVENTION In recent times it has become necessary in many instances to provide cooling means to dissipate the heat generated in electric fuses. It is known to provide electric fuses with water jackets for the purpose of dissipating the heat generated in the fuses. The cooling effectiveness of external water jackets is, however, relatively limited. The copending patent application of Frederick J. Kozacka filed Dec. 10, 1970 Ser. No. 96,76l for System of Fluid Cooled Fuses discloses a fuse structure making it possible to effectively cool electric fuses. This fuse structure is relatively simple as long as its rated voltage is relatively small, and becomes more complex as its voltage rating is increased. It does not lend itself to fuses having a relatively high voltage rating, e.g., fuses having a voltage rating of 1,000 volts, or

more.

The present invention refers to a fuse structure whose cooling efficiency is high and that can be applied for both small and high voltage ratings.

SUMMARY OF THE INVENTION Fuses embodying this invention include a tubular casing of insulating material and means of insulating material defining a fluid passageway arranged inside of, and in coaxial relation to, said casing. A pair of annular terminal elements is arranged adjacent the end of said casing and closes the space bounded by said casing and said fluid passageway defining means. This space is filled with a pulverulent arc-quenching filler. Ribbon fuse link means within said filler interconnect conductively said pair of terminal elements, and are arranged in close proximity to the radially outer surface of said fluid passageway defining means to maximize heat flow from said ribbon fuse link means across said fluid passageway defining means and to substantially preclude interposition of said filler between said fluid passageway defining means and said ribbon fuse link means. The fuse structure further includes annular clamping means of electric insulating material having BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is substantially a longitudinal section of a fuse embodying this invention taken along I-I of FIG. 2;

FIG. 2 is substantially a cross-section of the structure shown in FIG. 1 taken along IIII of FIG. 1;

FIG. 3 is an end view of the structure shown in FIGS. 1 and 2; and

FIG. 4 is an isometric view of a ribbon fuse links structure and adjacent parts which may be substituted for the ribbon fuse link structure of FIGS. 1 and 2.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION Reference numeral 1 has been applied in the drawings to indicate a tubular casing of an electric insulating material as, for instance, a melamine glass-clothlaminate, and reference numeral 2 has been applied to indicate a fluid flow passageway defining means of electric insulating material arranged inside of easing l and in coaxial relation to the latter. A pair of annular terminal elements, or terminal plugs, 3 is arranged adjacent the ends of casing l and closes the space bounded by casing 1 and fluid passageway defining means 2. Plugs 3 are press-fitted into casing l and firmly held in position by transverse steel pins. Each terminal plug 3 has a central, axially extending bore 3' imparting to it the aforementioned annular shape. The fluid passageway means 2 is formed by a length of insulating tubing, e.g., a length of tubing of melamine glasscloth-laminate press fitted into the bores 3' of terminal plugs 3. The length of tubing forming fluid passageway means 2 extends slightly beyond the axially outer end surfaces of terminal plugs 3. The toroidal space bounded by casing l and the lengthof tubing 2 is filled with a pulverulent arc-quenching filler 4, preferably quartz sand. A plug 3" closes an eccentric hole in at least one of terminal plugs 3 by which the pulverulent arch-quenching filler 4 may be filled into the aforementioned toroidal space. Reference numeral 5 has been applied to indicate several ribbon fuse link means within arc-quenching filler 4 conductively interconnecting the terminal elements, or terminal plugs, 3. The ribbon fuse link means 5 are arranged in close proximity to the radially outer surface of fluid passageway defining means 2 to maximize heat flow away from ribbon fuse link means 5 across part 2, and to substantially preclude interposition of particles of filler 4 between parts 2 and 5. This is of considerable importance to maximize heat exchange between a cooling medium flowing through part 2 as indicated by arrows and the ribbon fuse link means 5. In order to optimize heat exchange ribbon fuse link means 5 are preferably in physical engagement with the radially outer surface of the length of tubing 2. Though some arc-quenching fillers are relatively good conductors of heat, interposition of an arc-quenching filler between a fuse link and a cooling medium tends to greatly reduce the cooling effectiveness of the latter, particularly if there are relatively large, air filled interstices between the particles of the arc-quenching filler. Fuse link means 5 include an axially inner portion 5 defining a plurality of serially related points of reduced cross-sectional area or necks 5". Ribbon fuse link means 5 further include connector tabs 5" at the ends of said axially inner portion 5. The connector tabs 5" enclose with the axially inner fuse link portion 5' an angle of about and they abut against the axially inner end surfaces 3" of terminal plugs 3. Connector tabs 5" may either be soldered or spot welded to the end surfaces 3".

If a fuse is intended for a relatively high voltage rating its fuse link must be relatively long and include relatively many serially related points of reduced cross-sectional area, or necks. In such instances it is necessary, or desirable, to clamp fuse link means 5 against the radially outer surface of fluid passageway means 2. As

shown in the drawings ribbon fuse link means are clamped by annular hoop-like clamping means 6 against part 2. Clamping means 6 are made of a synthetic resin glasscloth laminate, preferably a laminate of melamine-glass-cloth and radially slotted in order to make it possible to be readily mounted on part 2 and fuse link means 5. Clamping means 6 are limited to discrete points of fuse link means 5, and separate these discrete points from the surrounding pulverulent arc-quenching filler 4. Thus parts 6 perform simultaneously two functions, i.e., they keep fuse link means 5 in close proximity to the radially outer surface of part 2 and they tend to stabilize the arc voltage by separating discrete zones of fuse link means 5 from filler 4. The theory underlying this way of stabilizing the arc voltage generated incident to blowing of the fuse is more fully set forth in U.S. Pat. No. 2,964,604 to RC. Jacobs, Jr. et al., Dec. 13, 1960 for Current-Limiting Fuse Having Compound Arc-Voltage Generating Means to which patent reference may be had for further details regarding the stabilization of the arc-voltage which may be achieved with the structure of FIGS. 1 and 2.

It will be apparent from the foregoing that the cooling action of the structure of FIGS. 1 and 2 is predicated on heat flow in radial direction or, to be more specific, radially inwardly directed heat flow. This makes it possibleto use in the structure fuse links of any desired length and for any desired voltage rating. The close proximity of cooling medium and fuse link means maximize the temperature gradient between cooling means and fuse link means. The cooling fluid is preferably a liquid, but gaseous cooling media may be used in connection with the structure of FIGS. 1 and 2, if desired. FIG. 4 shows a tubular ribbon fuse link 5a formed by a single stamping wound to conform with the shape of the external, or radially outer surface of fluid conduit 2a, and intended to hug the latter. The fuse link means 5 of FIGS. 1 and 2 may be replaced by the fuse link structure 50 of FIG. 4 without affecting the mode of cooling of the fuse as explained above. Though FIG. 4 shows an incomplete structure, it will be apparent that it refers but to a modification of that shown in FIGS. 1-3. The same reference characters with an a added have been applied in FIG. 4 to indicate like parts as in FIGS. 1-3 and, therefore, FIG. 4 does not call for further description.

If made of an organic insulating material link support 2 is not subject to ageing because its temperature rise may be kept within desired limits by the flow of cooling medium through it. There is a tendency that the temperature of part 2 be less than that of casing 1 in spite of the close proximity of hot ribbon fuse link means 5 to the former and the relative remoteness of hot ribbon fuse link means 5 from the latter.

The fuse of FIGS. 1-4 may be inserted in any desired conventional way into an electric circuit. As shown in FIGS. 1 and 2 the terminal plugs 3 are provided with blade contacts 7 (of which the axially outer portions are broken away) for insertion of the fuse into an appropriate fuse holder structure.

I claim as my invention:

1. A convention cooled electric fuse including a tubular casing of electric insulating material;

b. means of insulating material defining a fluid passageway arranged inside of and in coaxial relation to said casing;

c. a pair of annular terminal elements arranged adjacent the ends of said casing and closing the space bounded by said casing and by said fluidpassageway-defining means;

d. a pulverulent arc-quenching filler inside said space;

e. ribbon fuse link means within said filler conductively interconnecting said pair of terminal elements and arranged in close proximity to the radially outer surface of said fluid-passageway-defining means to maximize heat flow from said ribbon fuse link means across said fluid-passagewaydefining means and to substantially preclude interposition of said fillerbetween said fluidpassageway-defining means and said ribbon fuse link means;

f. annular clamping means of electric insulating material having radially inner relatively wide cylindrical surfaces and axially outer relatively narrow edges surrounding said ribbon fuse link means with said relatively wide cylindrical surfaces thereof, clamping said ribbon fuse link means against the radially outer surface of said fluid-passagewaydefining means and precluding access of said filler to portions of said ribbon-fuse-link means coextensive with said radially inner relatively wide cylindrical surfaces of said clamping means while allowing other portions of said ribbon-fuse-link means to be physically engaged by said tiller.

2. A fuse as specified in claim I wherein said fluidpassageway-defining means is of melamine glass-clothlaminate and wherein said annular clamping means are of a laminate of melamine-glass-cloth, are radially slotted and separate discrete zones of said ribbon fuse link means from said filler.

3. A convection cooled electric fuse including a. a fuse link support of insulating material defining a fluid passageway open at both ends thereof;

b. a pair of terminal plugs arranged in spaced coaxial relation and having central axially extending holes, said fuse link support projecting through said holes beyond the axially outer end surfaces of said pair of terminal plugs;

c. a tubular casing of insulating material mounted on said pair of terminal plugs, said fuse link support and said casing jointly defining a toroidal space;

d. a body of quartz sand inside said space;

e. ribbon fuse link means having a plurality of serially related points of reduced cross-sectional area, said ribbon fuse link means hugging the radially outer surface of said fuse link support and having terminal tabs bent about degrees and abutting against the axially inner end surfaces of said pair of terminal plugs; and

g. substantially annular hoop-like clamping means of a synthetic resin-glass-cloth-laminate for maintaining said ribbon fuse link means in physical engagement with the radially outer surface of said fuse link support, said clamping means having radially inner relatively wide cylindrical surfaces immediately adjacent said fuse link means and axially outer relatively narrow edges, and said clamping means being restricted to discrete points of said ribbon fuse link means so as to preclude access of said body of quartz sand to said ribbon fuse link means at other points thereof than said discrete points. 

1. A convention cooled electric fuse including a tubular casing of electric insulating material; b. means of insulating material defining a fluid passageway arranged inside of and in coaxial relation to said casing; c. a pair of annular terminal elements arranged adjacent the ends of said casing and closing the space bounded by said casing and by said fluid-passageway-defining means; d. a pulverulent arc-quenching filler inside said space; e. ribbon fuse link means within said filler conductively interconnecting said pair of terminal elements and arranged in close proximity to the radially outer surface of said fluidpassageway-defining means to maximize heat flow from said ribbon fuse link means across said fluid-passageway-defining means and to substantially preclude interposition of said filler between said fluid-passageway-defining means and said ribbon fuse link means; f. annular clamping means of electric insulating material having radially inner relatively wide cylindrical surfaces and axially outer relaTively narrow edges surrounding said ribbon fuse link means with said relatively wide cylindrical surfaces thereof, clamping said ribbon fuse link means against the radially outer surface of said fluid-passageway-defining means and precluding access of said filler to portions of said ribbon-fuse-link means coextensive with said radially inner relatively wide cylindrical surfaces of said clamping means while allowing other portions of said ribbon-fuse-link means to be physically engaged by said filler.
 2. A fuse as specified in claim 1 wherein said fluid-passageway-defining means is of melamine glass-cloth-laminate and wherein said annular clamping means are of a laminate of melamine-glass-cloth, are radially slotted and separate discrete zones of said ribbon fuse link means from said filler.
 3. A convection cooled electric fuse including a. a fuse link support of insulating material defining a fluid passageway open at both ends thereof; b. a pair of terminal plugs arranged in spaced coaxial relation and having central axially extending holes, said fuse link support projecting through said holes beyond the axially outer end surfaces of said pair of terminal plugs; c. a tubular casing of insulating material mounted on said pair of terminal plugs, said fuse link support and said casing jointly defining a toroidal space; d. a body of quartz sand inside said space; e. ribbon fuse link means having a plurality of serially related points of reduced cross-sectional area, said ribbon fuse link means hugging the radially outer surface of said fuse link support and having terminal tabs bent about 90 degrees and abutting against the axially inner end surfaces of said pair of terminal plugs; and g. substantially annular hoop-like clamping means of a synthetic resin-glass-cloth-laminate for maintaining said ribbon fuse link means in physical engagement with the radially outer surface of said fuse link support, said clamping means having radially inner relatively wide cylindrical surfaces immediately adjacent said fuse link means and axially outer relatively narrow edges, and said clamping means being restricted to discrete points of said ribbon fuse link means so as to preclude access of said body of quartz sand to said ribbon fuse link means at other points thereof than said discrete points. 